db/recno/rec_search.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by the University of
  16  *      California, Berkeley and its contributors.
  17  * 4. Neither the name of the University nor the names of its contributors
  18  *    may be used to endorse or promote products derived from this software
  19  *    without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  31  * SUCH DAMAGE.
  32  */
  33
  34 #if defined(LIBC_SCCS) && !defined(lint)
  35 static char sccsid[] = "@(#)rec_search.c        8.4 (Berkeley) 7/14/94";
  36 #endif /* LIBC_SCCS and not lint */
  37
  38 #include <sys/types.h>
  39
  40 #include <errno.h>
  41 #include <stdio.h>
  42
  43 #include <db.h>
  44 #include "recno.h"
  45
  46 /*
  47  * __REC_SEARCH -- Search a btree for a key.
  48  *
  49  * Parameters:
  50  *      t:      tree to search
  51  *      recno:  key to find
  52  *      op:     search operation
  53  *
  54  * Returns:
  55  *      EPG for matching record, if any, or the EPG for the location of the
  56  *      key, if it were inserted into the tree.
  57  *
  58  * Returns:
  59  *      The EPG for matching record, if any, or the EPG for the location
  60  *      of the key, if it were inserted into the tree, is entered into
  61  *      the bt_cur field of the tree.  A pointer to the field is returned.
  62  */
  63 EPG *
  64 __rec_search(t, recno, op)
  65         BTREE *t;
  66         recno_t recno;
  67         enum SRCHOP op;
  68 {
  69         register indx_t index;
  70         register PAGE *h;
  71         EPGNO *parent;
  72         RINTERNAL *r;
  73         pgno_t pg;
  74         indx_t top;
  75         recno_t total;
  76         int sverrno;
  77
  78         BT_CLR(t);
  79         for (pg = P_ROOT, total = 0;;) {
  80                 if ((h = mpool_get(t->bt_mp, pg, 0)) == NULL)
  81                         goto err;
  82                 if (h->flags & P_RLEAF) {
  83                         t->bt_cur.page = h;
  84                         t->bt_cur.index = recno - total;
  85                         return (&t->bt_cur);
  86                 }
  87                 for (index = 0, top = NEXTINDEX(h);;) {
  88                         r = GETRINTERNAL(h, index);
  89                         if (++index == top || total + r->nrecs > recno)
  90                                 break;
  91                         total += r->nrecs;
  92                 }
  93
  94                 BT_PUSH(t, pg, index - 1);
  95
  96                 pg = r->pgno;
  97                 switch (op) {
  98                 case SDELETE:
  99                         --GETRINTERNAL(h, (index - 1))->nrecs;
 100                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 101                         break;
 102                 case SINSERT:
 103                         ++GETRINTERNAL(h, (index - 1))->nrecs;
 104                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 105                         break;
 106                 case SEARCH:
 107                         mpool_put(t->bt_mp, h, 0);
 108                         break;
 109                 }
 110
 111         }
 112         /* Try and recover the tree. */
 113 err:    sverrno = errno;
 114         if (op != SEARCH)
 115                 while  ((parent = BT_POP(t)) != NULL) {
 116                         if ((h = mpool_get(t->bt_mp, parent->pgno, 0)) == NULL)
 117                                 break;
 118                         if (op == SINSERT)
 119                                 --GETRINTERNAL(h, parent->index)->nrecs;
 120                         else
 121                                 ++GETRINTERNAL(h, parent->index)->nrecs;
 122                         mpool_put(t->bt_mp, h, MPOOL_DIRTY);
 123                 }
 124         errno = sverrno;
 125         return (NULL);
 126 }